Mold composition for foundry use



United States Patent Ofilice 3,305,370 Patented Feb. 21, 1967 3,305,370 MOLD COMPOSITION FOR FOUNDRY USE James Beale, Nechells, Birmingham, England, assignor to Foseco International Limited, Birmingham, England, a British company No Drawing. Filed June 10, 1963, Ser. No. 286,527 Claims priority, application Great Britain, June 20, 1962, 23,813/ 62 4 Claims. (Cl. 106--38.5)

This invention relates to sand :products for use in foundry practice and to additives for sand for improving the properties thereof.

Sand is used for making foundry molds and since its intrinsic properties are not always entirely satisfactory various proposals have been made for obtaining the desired properties or improving the existing properties of the sand.

To be satisfactory, foundry sand for making metal casting molds and cores must have certain fundamental properties, thus:

(a) It should flow readily in order that it may fill recesses in pat-terns use-d for making sand molds. It should thus be able to flow readily in any direction against the pattern surface since in this way a better surface finish to the sand mold, and accordingly to the casting made in it, is obtained. One of the principal factors altecting flowability is the nature and amount of bonding agent used to bond the sand :particles together.

(b) The sand should be capable of being bonded to a tough structure which is rigid and easily handleable. It has been proposed to include starch with the sand to improve the toughness but this additive tends to affect adversely the fiowability of the sand.

(c) The molded sand should retain its moisture content with as little loss as possible for a substantial period of time and with a varying ambient temperature. Molds are not always closed or cast immediately after their assembly and removal of the pattern and there is accordingly danger of loss of moisture. The rate of moisture loss is usually controlled by the nature of the bonding agent used.

Accordingly, to obtain satisfactory results, the sand mix used should be readily fiowable and should bond to a tough shape and with little tendency to lose moisture. Defects in castings can frequently be traced to inadequacy of the sand mix in one or more of these features.

The present invention is concerned with a sand mix which more closely approaches the desideratum noted above. According to the present invention a sand mix for the production of molds and the like for foundry casting comprises sand and a small proportion of an additive comprising a surface-active substance and a substance which will form an aqueous gel or highly viscous solution.

The surface-active agent may be any wetting agent known per se but since cheapness is essential for the purpose in question, cheap detergent materials such as soaps and the cruder synthetic detergents are adequate. A particularly useful material is palm oil soap powder which is a very impure soap containing about 37% of soda ash. Synthetic detergents may be anion active, cation-active or non-ionic and examples are the well known range of long chain al-kyl sulphates, alkyl aryl sulphonates, long chain alkyl trimethyl ammonium salts, and condensation prodacts of ethylene oxide an-d/ or propylene oxide with phenols or aromatic amino compounds.

The substance which gels in water or which gives aqueous solutions of very high viscosity may be, for example, a water soluble or swellable cellulose derivative, e.g. sodium carboxy methyl cellulose, or an alginate, e.g. sodium alginate. A wide variety of such substances is known, e.g. from the art of manufacturing cosmetic creams. It is desirable that the selected substance should not be one which causes flocculation of clay if clay is also present in the sand mix.

The additive may contain, for example, from 599% by weight of the surface active agent and from l% of the agent which gives a high viscosity solution in water. It may be added to the sand in a proportion, for example, of 0.022.0% by weight of the sand.

Other additives may be included in the sand mix, e.g. fully chlorinated hydro-carbons which serve to improve the flowability of the metal as it enters the mold cavities (probably by providing a non-oxidising atmosphere with in the mold).

A specific additive according to the invention consists, for example, of:

Percent by weight Palm oil soap powder 66 Crude sodium alginate 33 Hexachlorethane 1 Addition of this additive to sand in a proportion of 0.1% of the weight of the sand affords a sand mix of improved flow-ability and regularity of density, of improved toughness and improved moisture retention. Accordingly, molds made from it have an improved surface and afford improved molding properties, so that there is a reduced tendency to casting defects due to inclusions, arising from crushing or friability of the mold surface or irregular mold expansion. Sand adhesion to the casting is substantially reduced, even when the mix also contains clay of a low sintering .point.

It is to be observed that the improved results are only obtained by using in the additive both the surface-active compound and the substance which gives a gel a high Viscosity solution in water; the use of a surface active agent alone does not afford such good results.

I claim as my invention;

1. A sand mix for the production of molds and the like for foundry casting which consists essentially of sand and 0.02 to 2.0% by weight of an additive comprising 5 to 99% by weight of .palm oil soap powder and 1 to 95% by weight respectively, of a gel-forming material selected from the class consisting of water soluble cellulose ethers and alginates.

2. A sand mix for the production of molds and the like for foundry casting which consists essentially of sand and 0.02 to 2.0% by weight of an additive comprising 5 to 99% by weight of palm oil soap powder and l to 95% by weight, respectively, of sodium carboxy-methyl cellulose.

3. A sand mix for the production of molds and the like for foundry casting which consists essentially of sand and 0.02 to 2.0% by weight of an additive comprising 5 to 99% by weight of palm oil soap powder and 1-95% by weight, respectively, of sodium alginate.

References Cited by the Examiner UNITED STATES PATENTS Wolf 106-38.5 XR Moren 106-38.5 McCord 106-3824 XR Beersma et a1 106206 4 3,034,186 5/1962 Holshouser 22200.1 3,146,113 8/1'964 Middleton et a1. 1O6-38.23 3,179,523 4/1965 Moren 10638.5 XR

FOREIGN PATENTS 919,194 9/1959 Great Britain.

ALEXANDER H. BRODMERKEL, Primary Examiner.

MORRIS LIEBMAN, Examiner.

J. EVANS, Assistant Examiner. 

1. A SAND MIX FOR THE PRODUCTION OF MOLDS AND THE LIKE FOR FOUNDRY CASTING WHICH CONSISTS ESSENTIALLY OF SAND AND 0.02 TO 2.0% BY WEIGHT OF AN ADDITIVE COMPRISING 5 TO 99% BY WEIGHT OF PALM OIL SOAP POWDER AND 1 TO 95% BY WEIGHT RESPECTIVELY, OF A GEL-FORMING MATERIAL SELECTED FROM THE CLASS CONSISTING OF WATER SOLUBLE CELLULOSE ETHERS AND ALGINATES. 